So I have Windows 7 64bit with 2x2 Gb at 1333 Mhz Kingston RAM. Motherboard is Gigabyte Ultra Durable 3 P55-US3L, and CPU Intel I5 650 (2x3.2 Ghz). I want to upgrade RAM for now. I have a friend that runs a Computer store and asked him for recommendation. He said to me that if I leave my current RAM memories and add 4 GB at lets say 1600 MHz, they will work at 1333 Mhz. Same thing will happen if I remove the old ones and insert 8 GB or 2x4 GB at 1600 MHz - they will remain locked at 1333 Mhz which is weird to me. In order to unlock the higher speed I need to overclock my CPU. I checked my motherboard specifications and it says that it supports RAM speeds up to 2200 MHz. So the question is, is it true that if I insert faster modules and remove the old ones, the speed will remain locked at 1333 MHz? Is the difference between 1333 and 1600 MHz or even faster noticeable? I'm asking all of this because the price difference between 1333 and 1600 MHz exists, and not to mention the faster ones. Thank you for reading!